Hydroxypolybenzimidazole Electrolyte with Excellent Stability for High Power Density All-Solid-State Supercapacitors

A high-performance solid-state electrolyte was obtained based on hydroxypolybenzimidazole grafting with the anion exchange silica precursor (AESP). The introduction of rigid polymer chains and quaternary ammonium groups not only increases mechanical strength but also greatly improves electrical conductivity. The obtained membranes maintain excellent mechanical properties about 23.1 MPa even after doping with 3.5 M KOH for 72 h and high hydroxide conductivity of about 0.077 S/cm (remaining above 0.043 S/cm after 216 h). There are few studies on the application of AEMs as electrolytes for all-solid-state supercapacitors (ASCs) currently. Therefore, the attempt was made to assemble the ASCs by using the PBIOH-AESP X membranes and activated carbon (AC) electrodes. The supercapacitor exhibits remarkable cycle stability (the capacitance retention rate is 87% and the Coulomb efficiency is 94.2% after 6000 GCD cycles) and a very high power density (82.32 kW/kg). In addition, three series connected supercapacitors illuminated a 3 V LED for more than 20 s. These results indicate that the polymer membranes are promising electrolytes for supercapacitors.